high performance walls - solutions for thermal bridging

High Performance Wall Assemblies – Designs to Minimize Thermal Bridging & Maximize PerformancePHILADELPHIA BUILDING ENCLOSURE COUNCIL – SEPT 15, 2015

GRAHAM FINCH, MASC, P.ENG – PRINCIPAL, RDH BUILDING SCIENCES INC.

“RDH Building Sciences” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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High Performance Wall Assemblies – Designs that Minimize Thermal Bridging & Maximize Performance (1 AIA/CES HSW CREDIT)

This 1 hour educational session will cover the latest in building enclosure technology for high performance wall assembly designs. Presented by one of North America’s leading building science research engineers, Graham Finch of RDH Building Sciences will provide an overview of emerging wall assemblies and components that provide durable, cost effective and thermally efficient performance.

Recent energy code changes will be reviewed including an opportunity to discuss solutions to meet these more stringent requirements. Strategies to construct highly insulated wall assemblies and minimize thermal bridges will be presented, including an in-depth assessment of various cladding supports. Several case studies will be incorporated to illustrate how these emerging technologies have been utilized in new and existing buildings.

Course Outline

Learning ObjectivesAt the end of this program, participants will be able to:

1. Review recent changes to local Energy Codes that impact wall assembly design strategies

2. Understand the building enclosure design requirements for wall assemblies and how the selection of all the right materials together are critical to reliable long-term performance.

3. Learn about several emerging technologies that are being used for the construction of highly insulated wall assemblies.

4. Learn about different strategies for attaching cladding through exterior insulation and how the different systems compare in terms of thermal performance, ease of installation and cost

Outline Drivers for Improved Building Enclosures &

Trends in Exterior Wall Designs Evolution of Designs, Trials and Lessons Learned Introduction to New & Innovative Cladding

Attachment Strategies Thermal Performance Comparison

What do you See?

COLD

HOT

What do you see?

What do you see?

Industry Trends in Building Enclosure Designs

Trend towards more efficiently insulated building enclosures due to higher energy code targets and uptake of passive design strategies At a point where traditional wall/roof

designs are being replaced with new ones Seeing many new building materials,

enclosure assemblies and construction techniques

Greater attention paid to reducing thermal bridging & use of effective R-values instead of nominal insulation R-values

Optimization of cladding attachments for both structural and thermal performance

More & more insulation is being used

US Codes now require consideration of Effective R-values

Nominal R-values are the rated R-values of insulation materials which do not include impacts of how they are installed For example 5.5” R-20 batt

insulation or 2” R-10 rigid foam insulation

Effective R-values are the actual R-values of assemblies which include for the impacts thermal bridging through the insulation For example nominal R-20 batts

within 2x6 steel studs 16” o.c. becoming ~R-9 effective, or in wood studs ~R-15

Code Shift to Effective R-values

From Code Minimum to Next Generation

Energy codes outline minimum thermal performance criteria based on general climate zone classifications

Energy Standards & International Codes: ASHRAE 90.1, IECC Municipal & State Adoptions

w/ Modifications Green Building Codes (ASHRAE

189.1, IGCC) and Voluntary Programs (Passive House, LEED) raise the bar

Wall Effective R-value/U-values are an integral part of energy code compliance

Energy Codes Targets for Commercial Buildings – IECC 2012

IECC

201

2

Climate Zone

Above Grade Walls: Mass, Steel, Wood Min. Eff. R-value

Roofs: Sloped, FlatMin. Eff. R-value

7 16.4, 15.6, 19.6 47.6, 35.7

6 12.8, 15.6, 19.6 47.6, 31.3

5 & 4C 12.8, 15.6, 15.6 47.6, 25.6

4 A/B 9.6, 15.6, 15.6 37.0, 25.6

3 9.1, 15.6, 15.6 37.0, 20.8

2 7.0, 13.0, 15.6 37.0, 20.8

1 7.0, 13.0, 15.6 37.0, 20.8

Clim

ate

Zone

Some state by state & municipal differences depending on year of energy code adoption.

Based on Maximum Effective Assembly U-value Tables.

Residential Building R-values similar or in some cases slightly higher

R-15.6 Steel Stud Wall?

As bad (here), or as good as you can practically build – you just can’t get an effective R-15.6 (or even lower R-13) out of stuffing insulation between steel studs – no matter what depth the studs may be.

Also not R-15.6 Steel Framed Walls

No matter the insulation type, you also cannot practically get to >R-15.6 with continuous steel girts through exterior insulation

Performance Targets & New Expectations

In Northeast (Climate Zones 4-7) minimum effective R-value design targets are in range of: R-15 to R-30 effective for walls R-25 to R-50 effective for roofs

Green or more energy efficient building programs including Passive House, R-value targets in range of: R-25 to R-50+ effective for walls R-40 to R-80+ effective for roofs

Plus other drivers – air-tight, thermal comfort, passive design, mould-free

Strategies for More Highly Insulated Wall Assemblies

Where to Add More Insulation in Walls?

Stuff It?

Wrap It?

Getting to Higher Insulation Levels in Exterior Walls

Base 2x6 Framed Wall <R-16 (wood)

Exterior InsulationR-20 to R-60+

Deep Stud, Double Stud, SIPSR-20 – R-80+

Split Insulation R-20 to R-60+

Interior InsulationR-20 to R-30+

Issues: cladding attachment, thickness

Issues: thermal bridging, thickness, durability

Issues: thickness, durability, interior detailsIssues: cladding attachment, material selection

There is Way More than One Way to Get There…

Cladding Attachment & Exterior Insulation

Exterior insulation is only as good as the cladding attachment strategy

What attachment systems work best?

What is and how to achieve true continuous insulation (ci) performance?

What type of insulation?

Drivers for Exterior Insulation Innovation

Drivers for Exterior Insulation InnovationPre-Rehabilitation – Stud Insulated, Lots of Thermal Bridging

Post-Rehabilitation – Exterior Membrane & Fully Exterior Insulated

Early Projects & Trials

Early Projects & Lessons Learned

Early Projects & Lessons Learned

A Desire to Do Better

Evolution & Innovation of New Systems

Little Nuances & Details to Resolve

FILL AROUND CLIPS

HOW TO RETAIN INSULATION? CORNER SUPPORTS?

HOW TOOPTIMIZE CLIPS & OTHER METALWORK?

PENETRATIONS AND DETAILS?

Further Evolution and Additional Testing

PROTYPING IDEAS WITH INTERN STUDENTS

Other Considerations - NFPA 285

Full-scale fire test developed initially by foam plastic insulation industry in late 1970s in response to non-combustible construction requirements within the IBC

Intent is to prevent fire propagation up the outside of a tall building

EIFS, combustible claddings and WRBS added to test requirements in addition to foam plastic insulation requirements between 2000 and 2012

NFPA 285 Triggers & Industry Response

Foam Plastics in the wall assembly all buildings (any height)

Combustible claddings in buildings over 40 feet High Pressure Laminates Fiber Reinforced Polymers Metal Composite Materials EIFS

Combustible WRBs in buildings over 40 feet

Industry Response = NFPA 285 Tested Assemblies or Non-Combustible Insulation, Claddings & WRBs

Passing test with mineral wool & fiberglass clips

Choosing a Cladding Attachment System

Exterior Insulation & Cladding Attachment Considerations

Cladding weight & gravity loads Wind & seismic loads Back-up wall construction (wood, concrete, steel)

Attachment from clip/girt back into structure (studs, sheathing, or slab edge)

Thickness of exterior insulation Use of rigid, semi-rigid or spray-applied insulation

Ability to fasten cladding supports through face Ability to ft insulation tightly around cladding supports

R-value target, tolerable thermal loss from supports Cladding orientation (panel, vertical, horizontal) Ease of attachment of cladding – returns, corners, returns etc. Combustibility requirements

Many Cladding Attachment Options & Counting

Vertical Z-girts Horizontal Z-girts Crossing Z-girts Galvanized/Stainless Clip & Rail

Aluminum Clip & Rail Long Screws through Insulation

Non-Conductive Clip

& Rail

Thermally Improved Clip &

Rail

Types of Insulation & Cladding Attachment

Continuous Girts – Rigid or Semi-rigid boards or spray-foam (i.e. almost anything works)

Intermittent Clip & Rail Systems – Semi-rigid boards or spray-foam (i.e. flexibility & ease of installation is key)

Screws through Insulation – rigid insulation boards (i.e. stiff enough to support compression load)

Cladding Attachment: Continuous Wood Framing

~15-30% loss in R-value

Cladding Attachment: Vertical Steel Z-Girts

~60-80%+ loss in R-value

Cladding Attachment: Horizontal Steel Z-Girts

~50-70%+ loss in R-value

Cladding Attachment: Horizontal Steel Z-Girts

Cladding Attachment: Crossing Steel Z-Girts

~40-60%+ loss in R-value

Cladding Attachment: Crossing Z-Girts

Cladding Attachment: Clip & Rail, Steel

~25-50% loss in R-value for galvanized, 15-35% for stainless steel (4x less conductivity)

Cladding Attachment: Clip & Rail, Steel

Cladding Attachment: Clip & Rail, Stainless Steel

Cladding Attachment: Clips w/ Diagonal Z-Girts

Cladding Attachment: Metal Panel Clips (Steel)

Cladding Attachment: Adjustable Steel Clip & Rail

Cladding Attachment: Adjustable Steel Clip & Rail

Other Steel & Aluminum Cladding Clip & Rail Technologies

Cladding Attachment: Aluminum Clip & Dual Girt

~30-50% loss in R-value (spacing dependant)

Cladding Attachment: Clip & Rail, Isolated Galvanized

Isolate the metal, improve the performance

~10-40% loss in R-value (spacing dependant)

Cladding Attachment: Clip & Rail, Isolated Galvanized

Cladding Attachment: Clip & Rail, Fiberglass

Remove the metal – maximize the performance

~5-30% loss in R-value (spacing & fastener type dependant)

Cladding Attachment: Clip & Rail, Fiberglass

Structural & Thermal Calculator - http://www.cascadiawindows.com/cascadia-clip-calculator

Clip & Rail and Stucco Considerations

Intermediate stucco backer board support

3 coat stucco application over reinforcing mesh and rigid backerboard (3ply asphalt board or cement board) to span rainscreen cavity

Cladding Attachment: Clip & Rail Fiberglass (No Screws)

Cladding Attachment: Other Discrete Engineered

12’

10’

Insulation Retainment/Attachment Fasteners

Why You Need to Mechanically Retain Exterior Insulation

Cladding Attachment: Screws through Insulation

Longer cladding Fasteners directly through rigid insulation (up to 2” for light claddings)

Long screws through vertical strapping and rigid insulation creates truss – short cladding fasteners into vertical strapping Rigid shear block type connection

through insulation, short cladding fasteners into vertical strapping

Cladding Attachment: Screws Through Insulation

~5-25% loss in R-value (back-up wall, spacing & fastener type dependant)

Really Thick Insulation = Really Long Screws

10” Exterior Insulation

Insulated Metal Panels Fiberglass Girts Insulated Concrete Forms Structurally Insulated Panels &

Insulated Sheathing Panels Autoclaved Aerated Concrete

Other Systems & Technologies - No Clips

Adhered & Mechanically Attached EIFS

12” EPS insulation boards (blocks?) R-54

Cladding Attachment: Masonry Ties & Shelf Angles

Continuous shelf angles~50% R-value loss

Brick ties – 10-30% loss for galvanized ties, 5-10% loss for stainless steel

Shelf angle on stand-offsonly ~15% R-value loss

Effective R-value Summary of Various Cladding Support Systems

No PenetrationsStainless Screws

Galvanized Screws

Stainless ClipsFiberglass Clips

Thermally Isolated Galvanized ClipsGalvanized ClipsAluminum T-ClipHorizontal Z-GirtsVertical Z-Girts

0

20

Effec

tive

R-V

alue

[ft

²·°F

·hr/

Btu]

Nominal R-4.2/Inch Exterior Insulation Thickness[inches]

2” 4” 6” 8”

30

40

10

50

Base backup wall is 3 5/8” steel stud (empty) + exterior insulation

Galvanized Screws

Stainless Screws

Thermally Isolated Galvanized Clips

Fiberglass ClipsStainless Clips

Galvanized ClipsAluminum T-Clip

Horizontal Z-GirtsVertical Z-Girts

Perc

ent

Effec

tive

ness

of E

xter

ior

In

sula

tion

Percent Effectiveness of Exterior Insulation with Various Cladding Support Systems

02” 4” 6” 8”

20%

40%

60%

80%

100%

Nominal R-4.2/Inch Exterior Insulation Thickness[inches]

Percent Effectiveness of Exterior Insulation with Various Cladding Support Systems

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Stainless Steel Screws

Galvanized Screws

Fiberglass Clip

Stainless Steel Clip

Isolated Galvanized Clip

Intermittent Galvanized Clip

Aluminum T-Clip

Continuous Horizontal Z-Girt

Continuous Vertical Z-Girt

Percent Effectiveness of Exterior Insulation (Typical Range)

Effective R-Value vs Structural Capacity for Clips

0

20

40

60

80

100

120

0

5

10

15

20

25

30

35

0 2 4 6 8 10

Max

imum

Allo

wab

le W

ind

Load

[psf

]

Effec

tive

R-va

lue

[ft²•

°F•h

r/Bt

u]

Exterior Insulation Depth / Clip Size [in]

Thermal and Strucutral Performance of Clip System

263648

VerticalClip

Spacing

Structural

Thermal

http://www.cascadiawindows.com/cascadia-clip-calculator

Cladding Attachment Recommendations

Substrate

Cladding Type

Wood Backup (OSB/Plywood)

Steel Stud Backup

Concrete or Concrete Block Backup

Light weight (up to fiber cement panels, <10psf)

Clip & Rail good

Screws good

Clip & Rail good

Screws okay, but difficult to hit stud

Clip & Rail good

Screws can be difficult to install

Medium weight (stucco, cultured stone, 10-30 psf)

Clip & Rail good

Screws with shear block or engineered

Clip & Rail good

Screws with shear block or engineered

Clip & Rail good

Screws can be difficult to install

Heavy weight (Masonry, Stone Panels, >30 psf)

Gravity supports, anchors & engineered connections only

Gravity supports, anchors & engineered connections only

Gravity supports, anchors & engineered connections only

Cladding Attachment System Videos:

http://www.roxul.com/products/commercial/products/roxul+cavityrock

Exterior Insulation Installation Guide

http://www.roxul.com/products/residential/products/roxul+comfortboard+is

Commercial Installation Guide Coming Very Soon

Further Information

rdh.com

Discussion & QuestionsGraham Finch – gfinch@rdh.com – 604.873.1181

This concludes The American Institute of Architects Continuing Education Systems

Course

Graham Finch , Dipl.T, MASc, P.EngPrincipal, Building Science Research SpecialistRDH Building Sciences Inc. gfinch@rdhbe.com www.rdh.com

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